全文获取类型
收费全文 | 951篇 |
免费 | 90篇 |
国内免费 | 349篇 |
专业分类
安全科学 | 121篇 |
废物处理 | 32篇 |
环保管理 | 97篇 |
综合类 | 660篇 |
基础理论 | 141篇 |
污染及防治 | 175篇 |
评价与监测 | 82篇 |
社会与环境 | 50篇 |
灾害及防治 | 32篇 |
出版年
2024年 | 8篇 |
2023年 | 20篇 |
2022年 | 61篇 |
2021年 | 68篇 |
2020年 | 65篇 |
2019年 | 57篇 |
2018年 | 46篇 |
2017年 | 53篇 |
2016年 | 53篇 |
2015年 | 70篇 |
2014年 | 57篇 |
2013年 | 68篇 |
2012年 | 79篇 |
2011年 | 92篇 |
2010年 | 86篇 |
2009年 | 66篇 |
2008年 | 71篇 |
2007年 | 67篇 |
2006年 | 57篇 |
2005年 | 44篇 |
2004年 | 39篇 |
2003年 | 24篇 |
2002年 | 36篇 |
2001年 | 22篇 |
2000年 | 19篇 |
1999年 | 8篇 |
1998年 | 6篇 |
1997年 | 11篇 |
1996年 | 9篇 |
1995年 | 8篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1990年 | 3篇 |
1986年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有1390条查询结果,搜索用时 328 毫秒
441.
Suppression pheromone and cockroach rank formation 总被引:1,自引:0,他引:1
Although agonistic behaviors in the male lobster cockroach (Nauphoeta cinerea) are well known, the formation of an unstable hierarchy has long been a puzzle. In this study, we investigate how the unstable
dominance hierarchy in N. cinerea is maintained via a pheromone signaling system. In agonistic interactions, aggressive posture (AP) is an important behavioral
index of aggression. This study showed that, during the formation of a governing hierarchy, thousands of nanograms of 3-hydroxy-2-butanone
(3H-2B) were released by the AP-adopting dominant in the first encounter fight, then during the early domination period and
that this release of 3H-2B was related to rank maintenance, but not to rank establishment. For rank maintenance, 3H-2B functioned
as a suppression pheromone, which suppressed the fighting capability of rivals and kept them in a submissive state. During
the period of rank maintenance, as the dominant male gradually decreased his 3H-2B release, the fighting ability of the subordinate
gradually developed, as shown by the increasing odds of a subordinate adopting an AP (OSAP). The OSAP was negatively correlated
with the amount of 3H-2B released by the dominant and positively correlated with the number of domination days. The same OSAP
could be achieved earlier by reducing the amount of 3H-2B released by the dominant indicates that whether the subordinate
adopts an offensive strategy depends on what the dominant is doing. 相似文献
442.
生物转盘系统中短程硝化的实现 总被引:3,自引:1,他引:2
在生物转盘反应器接种普通好氧污泥,在进水COD浓度为300mg/L,氨氮浓度为15mg/L,pH7.5~8.0,室温条件下启动试验,挂膜成功后对盘面以表层异养菌为主的生物膜层进行亚硝酸盐氧化菌的驯化,通过不断提高进水氨氮负荷和控制较低的C/N,系统硝化反应经历了由弱→强→弱的变化,而氨氧化反应不断得到强化。64d时,当进水N/C比为3.75,COD和氨氮浓度分别为40mg/L和150mg/L,氨氮面积负荷为7.46g/m·2d,HRT=3.16h时,出水亚硝氮累积率达到56.7%,系统中实现了短程硝化反应,随着系统的稳定,亚硝氮平均累积率为80%,最高达95.8%;驯化过程中生物膜厚度由0.2cm增加到0.5cm,颜色也由浅黄色变成黄褐色,镜检发现微生物种类变少,钟虫和累枝虫等消失,膜体中间由大量的丝状体连接。 相似文献
443.
毒死蜱和三唑磷在膨润土和腐殖质上的热力学吸附及影响因素 总被引:3,自引:0,他引:3
采用平衡法研究膨润土和腐殖质对毒死蜱和三唑磷的吸附规律及影响因素.结果表明,腐殖质对2种农药的吸附能力均大于膨润土,毒死蜱和三唑磷在腐殖质上的吸附行为均可用Freundlich模型和Langmuir模型描述,相关系数分别为:R2(毒死蜱)0.9964和0.9963;R2(三唑磷)0.9989和0.9924;膨润土对2种农药的等温吸附线可用Langmuir模型拟合,相关系数为:R2=0.9957(毒死蜱)、R2=0.9989(三唑磷).pH条件、吸附时间和温度均对吸附有影响.腐殖质、膨润土混合吸附剂对2种农药的吸附平衡时间分别为:毒死蜱12h,三唑磷6h.腐殖质﹕膨润土质量比分别达12%和14%时对三唑磷和毒死蜱的吸附最为强烈并趋于饱和.通过计算不同温度各热力学参数ΔG、ΔH和ΔS,理论上证实该吸附为一自发的放热过程,在pH=6.0,温度为15℃时,吸附效果最佳. 相似文献
444.
445.
446.
长期以来,黑龙江三江自然保护区湿地由于人口的增长、经济开发活动频繁增加,社会公众和管理者对湿地的功能和综合价值缺乏足够的认知,对其只是索取,而缺乏有效的保护,致使湿地生态环境发生了重大变化,造成水环境污染严重,土壤沙化、盐碱化面积不断扩大,灾害性气候频繁发生,动植物等生物多样性急剧减少,这与中国可持续发展的战略主旨及世界潮流相悖.在此,对黑龙江三江自然保护区湿地的现存问题进行分析,以期通过完善区域专项立法、建立湿地专管机构和湿地管理专项资金、完善管理协调机制、建立湿地环境影响评价制度和生态补偿制度、完善环境保护相关法律责任等途径,切实做到对湿地的保护和开发利用并重. 相似文献
447.
449.
Based on community data (2012, 2020) of the Tianlong Mountain evergreen and deciduous broadleaved mixed forest plot in central Guizhou, China, the species composition, importance value index, diversity, and dynamic changes were estimated to explore the renewal and change characteristics of karst secondary forests. The results showed that: (1) the number of individual species in the investigated two hm2 plot encompassing 33 families and 55 genera, totaling 69 species decreased from 10 276 to 7837. Five families, 10 genera, and 18 species were newly added, while seven families, nine genera, and 11 species disappeared. The difference between the importance value indices of the species was obvious; that of Lithocarpus confinis (20.97–23.26) was much higher than that of other species. Except for some species, the overall inter-annual differences were not large, and the status of mesophytic and shaded species has increased. Life forms were dominated by small trees and shrubs or small trees, and the plant number density of different life forms is reduced. (2) The Margalef and Shannon-Wiener indices of shrubs were the largest, and the Pielou indices of shrubs or small trees were the largest. The composition of most life forms has increased; the diversity became richer; and the uniform distribution of individual species has increased, but the change was small. (3) With respect to the spatial distribution pattern, the species were generally clustered, and only a few were randomly distributed. The Cx, I, m*, CA, and G indices of the species were reduced, and those of some species were quite different. A tendency for aggregated distribution was observed over random distribution, but the aggregation degree of Lithocarpus sphaerocephala was still high. The PAI index of most species increased but was not obvious, whereas the K value changed irregularly. Overall, the species composition, importance value index, diversity, and spatial distribution pattern of the main species in this community have changed to some extent but without any significant fluctuations. L. sphaerocephala was still the dominant species in succession, and the species composition of the flora was stable. The restoration of vegetation and the development of the entire community are slow. © 2022 Science Press. All rights reserved. 相似文献
450.
Rong Cheng Yingying Zhang Tao Zhang Feng Hou Xiaoxin Cao Lei Shi Peiwen Jiang Xiang Zheng Jianlong Wang 《Frontiers of Environmental Science & Engineering》2022,16(8):108